The supply is fixed forever (denominator). The Bitcoin in circulation changes over time based on many factors. Including Bitcoin HODL’d by people, Bitcoin awarded to miners (think of it has someone is HODL’ing a portion of the 21 million and awarding them every 10 min as you say). Inflation of the money supply is, when you increase the denominator. The whole purpose of sound money is to have a fixed, scarce supply. And we all know, Bitcoin has a fixed supply of 21 million (the variables time and state of Bitcoin are not part of the denominator). It’s in the code. No inflation if you use the definitions of Austrian economics.